Sodium tanshinone IIA sulfonate protects vascular relaxation in ApoE-knockout mice by inhibiting the SYK-NLRP3 inflammasome-MMP2/9 pathway.

BACKGROUND: Hyperlipidemia damages vascular wall and serves as a foundation for diseases such as atherosclerosis, hypertension and stiffness. The NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome is implicated in vascular dysfunction associated with hyperlipidemia-induced vascular injury. Sodium tanshinone IIA sulfonate (STS), a well-established cardiovascular protective drug with recognized anti-inflammatory, antioxidant, and vasodilatory properties, is yet to be thoroughly investigated for its impact on vascular relaxant imbalance induced by hyperlipidemia. METHODS: In this study, we treated ApoE-knockout (ApoE-/-) mouse with STS and assessed the activation of the NLRP3 inflammasome, expression of MMP2/9, integrity of elastic fibers, and vascular constriction and relaxation. RESULTS: Our findings reveal that STS intervention effectively preserves elastic fibers, significantly restores aortic relaxation function in ApoE-/- mice, and reduces their excessive constriction. Furthermore, STS inhibits the phosphorylation of spleen tyrosine kinase (SYK), suppresses NLRP3 inflammasome activation, and reduces MMP2/9 expression. CONCLUSIONS: These results demonstrate that STS protects vascular relaxation against hyperlipidemia-induced damage through modulation of the SYK-NLRP3 inflammasome-MMP2/9 pathway. This research provides novel insights into the mechanisms underlying vascular relaxation impairment in a hyperlipidemic environment and uncovers a unique mechanism by which STS preserves vascular relaxation, offering valuable foundational research evidence for its clinical application in promoting vascular health.

Endothelial PAR2 activation evokes resistance artery relaxation.

Protease-activated receptor-1 & -2 (PAR1 and PAR2) are expressed widely in cardiovascular tissues including endothelial and smooth muscle cells. PAR1 and PAR2 may regulate blood pressure via changes in vascular contraction or relaxation mediated by endothelial Ca2+ signaling, but the mechanisms are incompletely understood. By using single-cell Ca2+ imaging across hundreds of endothelial cells in intact blood vessels, we explored PAR-mediated regulation of blood vessel function using PAR1 and PAR2 activators. We show that PAR2 activation evoked multicellular Ca2+ waves that propagated across the endothelium. The PAR2-evoked Ca2+ waves were temporally distinct from those generated by muscarinic receptor activation. PAR2 activated distinct clusters of endothelial cells, and these cells were different from those activated by muscarinic receptor stimulation. These results indicate that distinct cell clusters facilitate spatial segregation of endothelial signal processing. We also demonstrate that PAR2 is a phospholipase C-coupled receptor that evokes Ca2+ release from the IP3 -sensitive store in endothelial cells. A physiological consequence of this PAR2 signaling system is endothelium-dependent relaxation. Conversely, PAR1 activation did not trigger endothelial cell Ca2+ signaling nor relax or contract mesenteric arteries. Neither did PAR1 activators alter the response to PAR2 or muscarinic receptor activation. Collectively, these results suggest that endothelial PAR2 but not PAR1 evokes mesenteric artery relaxation by evoking IP3 -mediated Ca2+ release from the internal store. Sensing mediated by PAR2 receptors is distributed to spatially separated clusters of endothelial cells.

Independent endothelial functions of PIEZO1 and TRPV4 in hepatic portal vein and predominance of PIEZO1 in mechanical and osmotic stress.

BACKGROUND & AIMS: PIEZO1 and TRPV4 are mechanically and osmotically regulated calcium-permeable channels. The aim of this study was to determine the relevance and relationship of these channels in the contractile tone of the hepatic portal vein, which experiences mechanical and osmotic variations as it delivers blood to the liver from the intestines, gallbladder, pancreas and spleen. METHODS: Wall tension was measured in freshly dissected portal veins from adult male mice, which were genetically unmodified or modified for either a non-disruptive tag in native PIEZO1 or endothelial-specific PIEZO1 deletion. Pharmacological agents were used to activate or inhibit PIEZO1, TRPV4 and associated pathways, including Yoda1 and Yoda2 for PIEZO1 and GSK1016790A for TRPV4 agonism, respectively. RESULTS: PIEZO1 activation leads to nitric oxide synthase- and endothelium-dependent relaxation of the portal vein. TRPV4 activation causes contraction, which is also endothelium-dependent but independent of nitric oxide synthase. The TRPV4-mediated contraction is suppressed by inhibitors of phospholipase A2 and cyclooxygenases and mimicked by prostaglandin E2 , suggesting mediation by arachidonic acid metabolism. TRPV4 antagonism inhibits the effect of agonising TRPV4 but not PIEZO1. Increased wall stretch and hypo-osmolality inhibit TRPV4 responses while lacking effects on or amplifying PIEZO1 responses. CONCLUSIONS: The portal vein contains independently functioning PIEZO1 channels and TRPV4 channels in the endothelium, the pharmacological activation of which leads to opposing effects of vessel relaxation (PIEZO1) and contraction (TRPV4). In mechanical and osmotic strain, the PIEZO1 mechanism dominates. Modulators of these channels could present important new opportunities for manipulating liver perfusion and regeneration in disease and surgical procedures.

The Effects of Novel Triazolopyrimidine Derivatives on H2S Production in Lung and Vascular Tonus in Aorta.

INTRODUCTION: Hydrogen sulfide (H2S), known as a third gasotransmitter, is a signaling molecule that plays a regulatory role in physiological and pathophysiological processes. Decreased H2S levels were reported in inflammatory respiratory diseases such as asthma, chronic obstructive pulmonary disease, and pulmonary hypertension. H2S donors or drugs that increase H2S have emerged as novel treatments for inflammatory respiratory diseases. We previously showed that resveratrol (RVT) causes vascular relaxation and antioxidant effects by inducing H2S production. In the current study, we synthesized a new molecule Cpd2, as an RVT analog. We examined the effect of Cpd2 and its precursor chalcone compound (Cpd1) on H2S formation under both healthy and oxidative stress conditions in the lung, as well as vascular relaxation in the aorta. METHODS: Cpd2 synthesized from Cpd1 with microwaved in basic conditions. H2S formation was measured by H2S biosensor in the mice lungs under both healthy and pyrogallol-induced oxidative stress conditions in the presence/absence of H2S synthesis inhibitor aminooxyacetic acid (AOAA). The effect of compounds on vascular tonus is investigated in mice aorta by DMT myograph. RESULTS: RVT and Cpd2 significantly increased l-cysteine (l-cys) induced-H2S formation in the lung homogenates of healthy mice, but Cpd1 did not. Superoxide anion generator pyrogallol caused a decrease in H2S levels in mice lungs and Cpd2 restored it. Inhibition of Cpd2-induced H2S formation by AOAA confirmed that Cpd2 increases endogenous H2S formation in both healthy and oxidative stress conditions. Furthermore, we found that both Cpd1 and Cpd2 (10-8-10-4 M) caused vascular relaxation in mice aorta. DISCUSSION AND CONCLUSION: We found that Cpd2, a newly synthesized RVT analog, is an H2S-inducing molecule and vasorelaxant similar to RVT. Since H2S has antioxidant and anti-inflammatory effects, Cpd2 has a potential for the treatment of respiratory diseases where oxidative stress and decreased H2S levels are present.

Defining the reducing system of the NO dioxygenase cytoglobin in vascular smooth muscle cells and its critical role in regulating cellular NO decay.

In smooth muscle, cytoglobin (Cygb) functions as a potent nitric oxide (NO) dioxygenase and regulates NO metabolism and vascular tone. Major questions remain regarding which cellular reducing systems regulate Cygb-mediated NO metabolism. To better define the Cygb-mediated NO dioxygenation process in vascular smooth muscle cells (SMCs), and the requisite reducing systems that regulate cellular NO decay, we assessed the intracellular concentrations of Cygb and its putative reducing systems and examined their roles in the process of NO decay. Cygb and the reducing systems, cytochrome b5 (B5)/cytochrome b5 reductase (B5R) and cytochrome P450 reductase (CPR) were measured in aortic SMCs. Intracellular Cygb concentration was estimated as 3.5 µM, while B5R, B5, and CPR were 0.88, 0.38, and 0.15 µM, respectively. NO decay in SMCs was measured following bolus addition of NO to air-equilibrated cells. siRNA-mediated knockdown experiments indicated that âˆ¼78% of NO metabolism in SMCs is Cygb-dependent. Of this, ∼87% was B5R- and B5-dependent. CPR knockdown resulted in a small decrease in the NO dioxygenation rate (VNO), while depletion of ascorbate had no effect. Kinetic analysis of VNO for the B5/B5R/Cygb system with variation of B5 or B5R concentrations from their SMC levels showed that VNO exhibits apparent Michaelis-Menten behavior for B5 and B5R. In contrast, linear variation was seen with change in Cygb concentration. Overall, B5/B5R was demonstrated to be the major reducing system supporting Cygb-mediated NO metabolism in SMCs with changes in cellular B5/B5R levels modulating the process of NO decay.

Inhibitory Effects of Saururus chinensis Extract on Receptor for Advanced Glycation End-Products-Dependent Inflammation and Diabetes-Induced Dysregulation of Vasodilation.

Advanced glycation end-products (AGEs) and the receptor for AGEs (RAGE) are implicated in inflammatory reactions and vascular complications in diabetes. Signaling pathways downstream of RAGE are involved in NF-κB activation. In this study, we examined whether ethanol extracts of Saururus chinensis (Lour.) Baill. (SE) could affect RAGE signaling and vascular relaxation in streptozotocin (STZ)-induced diabetic rats. Treatment with SE inhibited AGEs-modified bovine serum albumin (AGEs-BSA)-elicited activation of NF-κB and could compete with AGEs-BSA binding to RAGE in a dose-dependent manner. Tumor necrosis factor-α (TNF-α) secretion induced by lipopolysaccharide (LPS)-a RAGE ligand-was also reduced by SE treatment in wild-type Ager+/+ mice as well as in cultured peritoneal macrophages from Ager+/+ mice but not in Ager-/- mice. SE administration significantly ameliorated diabetes-related dysregulation of acetylcholine-mediated vascular relaxation in STZ-induced diabetic rats. These results suggest that SE would inhibit RAGE signaling and would be useful for the improvement of vascular endothelial dysfunction in diabetes.

Novel Oxime Synthesized from a Natural Product of Senecio nutans SCh. Bip. (Asteraceae) Enhances Vascular Relaxation in Rats by an Endothelium-Independent Mechanism.

Senecio nutans Sch. Bip. and its constituents are reported to have antihypertensive effects. We isolated metabolite−1, a natural compound from S. nutans (4-hydroxy-3-(isopenten-2-yl)-acetophenone), and synthesized novel oxime − 1 (4-hydroxy-3-(isopenten-2-yl)-acetophenoxime) to evaluate their effect on vascular reactivity. Compounds were purified (metabolite−1) or synthetized (oxime−1) and characterized using IR and NMR spectroscopy and Heteronuclear Multiple Quantum Coherence (HMQC). Using pharmacological agents such as phenylephrine (PE) and KCl (enhancing contraction), acetylcholine (ACh), L-NAME (nitric oxide (NO) and endothelial function), Bay K8644-induced CaV1.2 channel (calcium channel modulator), and isolated aortic rings in an organ bath setup, the possible mechanisms of vascular action were determined. Pre-incubation of aortic rings with 10−5 M oxime−1 significantly (p < 0.001) decreased the contractile response to 30 mM KCl. EC50 to KCl significantly (p < 0.01) increased in the presence of oxime−1 (37.72 ± 2.10 mM) compared to that obtained under control conditions (22.37 ± 1.40 mM). Oxime−1 significantly reduced (p < 0.001) the contractile response to different concentrations of PE (10−7 to 10−5 M) by a mechanism that decreases Cav1.2-mediated Ca2+ influx from the extracellular space and reduces Ca2+ release from intracellular stores. At a submaximal concentration (10−5 M), oxime−1 caused a significant relaxation in rat aorta even without vascular endothelium or after pre-incubate the tissue with L-NAME. Oxime−1 decreases the contractile response to PE by blunting the release of Ca2+ from intracellular stores and blocking of Ca2+ influx by channels. Metabolite−1 reduces the contractile response to KCl, apparently by reducing the plasma membrane depolarization and Ca2+ influx from the extracellular space. These acetophenone derivates from S. nutans (metabolite−1 and oxime−1) cause vasorelaxation through pathways involving an increase of the endothelial NO generation or a higher bioavailability, further highlighting that structural modification of naturally occurring metabolites can enhance their intended pharmacological functions.

Castanea sativa Mill. bark extract cardiovascular effects in a rat model of high-fat diet.

Ellagitannins may have a beneficial impact in cardiovascular diseases. The aim of the study was to evaluate the effect of high-fat diet (HFD) and the efficacy of Castanea sativa Mill. bark extract (ENC) on cardiac and vascular parameters. Rats were fed with regular diet, (RD, n = 15), HFD (n = 15), RD + ENC (20 mg/kg/day by gavage, n = 15), and HFD + ENC (same dose, n = 15) and the effects on body weight, biochemical serum parameters, and inflammatory cytokines determined. Cardiac functional parameters and aorta contractility were also assessed on isolated atria and aorta. Results showed that ENC reduced weight gain and serum lipids induced by HFD. In in vitro assays, HFD decreased the contraction force of left atrium, increased right atrium chronotropy, and decreased aorta K+ -induced contraction; ENC induced transient positive inotropic and negative chronotropic effects on isolated atria from RD and HFD rats and a spasmolytic effect on aorta. In ex vivo experiments, ENC reverted inotropic and chronotropic changes induced by HFD and enhanced Nifedipine effect more on aorta than on heart. In conclusion, ENC restores metabolic dysfunction and cardiac cholinergic muscarinic receptor function, and exerts spasmolytic effect on aorta in HFD rats, highlighting its potential as nutraceutical tool in obesity.

Progesterone promotes endothelial nitric oxide synthase expression through enhancing nuclear progesterone receptor-SP-1 formation.

Progesterone exerts antihypertensive actions partially by modulating endothelial nitric oxide synthase (eNOS) activity. Here, we aimed to investigate the effects and mechanisms of progesterone on eNOS expression. First, human umbilical vein endothelial cells (HUVECs) were exposed to progesterone and then the eNOS transcription factor specificity protein-1 (SP-1) and progesterone receptor (PRA/B) expression were assessed by Western blotting and qRT-PCR. The interaction between SP-1 and PRA/B was next determined through coimmunoprecipitation assay. The chromatin immunoprecipitation assay and luciferase assay were used to investigate the relationship of PRA/B, SP-1, and eNOS promoter. At last, rats were intraperitoneally injected with progesterone receptor antagonist RU-486, and then the expression of eNOS and vasodilation function in thoracic aorta and mesenteric artery were measured. The results showed that progesterone could increase eNOS expression in HUVECs. Further study showed that progesterone increased PRA-SP-1 complex formation and facilitated PRA/B and SP-1 binding to eNOS promoter. Mutating SP-1 or PR-binding motif on eNOS promoter abolished the effect of progesterone on eNOS gene transcription. We also observed that progesterone receptor antagonist RU-486 reduced eNOS expression and impaired vasodilation in rats. Those results suggest that progesterone modulates eNOS expression through promoting PRA-SP-1 complex formation, and progesterone antagonist attenuates eNOS expression, leading to the loss of vascular relaxation.NEW & NOTEWORTHY Progesterone directly upregulated endothelial nitric oxide synthase (eNOS) expression in human endothelial cells. Progesterone augmented eNOS promoter activity through a progesterone receptor A- and specificity protein-1-dependent manner. Antagonism of the progesterone receptor reduced eNOS expression and impaired vasodilation in rats.

Imipridone enhances vascular relaxation via FOXO1 pathway.

Cardiovascular complications are a side effect of cancer therapy, potentially through reduced blood vessel function. ONC201 (TIC10) is currently used in phase 2 clinical trials to treat high-grade gliomas. TIC10 is a phosphatidylinositol 3-kinase (PI3K)/AKT/extracellular signal-regulated kinase (ERK) inhibitor that induces apoptosis via upregulation of TNF-related apoptosis-inducing ligand, which via stimulation of FOXO and death receptor could increase eNOS upregulation. This has the potential to improve vascular function through increased NO bioavailability. Our aim was to investigate the role of TIC10 on vascular function to determine if it would affect the risk of CVD. Excised abdominal aorta from White New Zealand male rabbits were cut into rings. Vessels were incubated with TIC10 and AS1842856 (FOXO1 inhibitor) followed by cumulative doses of acetylcholine (Ach) to assess vessel function. Vessels were then processed for immunohistochemistry. Incubation of blood vessels with TIC10 resulted in enhanced vasodilatory capacity. Combination treatment with the FOXO1 inhibitor and TIC10 resulted in reduced vascular function compared to control. Immunohistochemical analysis indicated a 3-fold increase in death receptor 5 (DR5) expression in the TIC10-treated blood vessels but the addition of the FOXO1 inhibitor downregulated DR5 expression. The expression of DR4 receptor was not significantly increased in the presence of TIC10; however, addition of the FOXO1 inhibitor downregulated expression. TIC10 has the capacity to improve the function of healthy vessels when stimulated with the vasodilator Ach. This highlights its therapeutic potential not only in cancer treatment without cardiovascular side effects, but also as a possible drug to treat established CVD.

Quercetin Exerts Age-Dependent Beneficial Effects on Blood Pressure and Vascular Function, But Is Inefficient in Preventing Myocardial Ischemia-Reperfusion Injury in Zucker Diabetic Fatty Rats.

Background: Quercetin (QCT) was shown to exert beneficial cardiovascular effects in young healthy animals. The aim of the present study was to determine cardiovascular benefits of QCT in older, 6-month and 1-year-old Zucker diabetic fatty (ZDF) rats (model of type 2 diabetes). Methods: Lean (fa/+) and obese (fa/fa) ZDF rats of both ages were treated with QCT for 6 weeks (20 mg/kg/day). Isolated hearts were exposed to ischemia-reperfusion (I/R) injury (30 min/2 h). Endothelium-dependent vascular relaxation was measured in isolated aortas. Expression of selected proteins in heart tissue was detected by Western blotting. Results: QCT reduced systolic blood pressure in both lean and obese 6-month-old rats but had no effect in 1-year-old rats. Diabetes worsened vascular relaxation in both ages. QCT improved vascular relaxation in 6-month-old but worsened in 1-year-old obese rats and had no impact in lean controls of both ages. QCT did not exert cardioprotective effects against I/R injury and even worsened post-ischemic recovery in 1-year-old hearts. QCT up-regulated expression of eNOS in younger and PKCε expression in older rats but did not activate whole PI3K/Akt pathway. Conclusions: QCT might be beneficial for vascular function in diabetes type 2; however, increasing age and/or progression of diabetes may confound its vasculoprotective effects. QCT seems to be inefficient in preventing myocardial I/R injury in type 2 diabetes and/or higher age. Impaired activation of PI3K/Akt kinase pathway might be, at least in part, responsible for failing cardioprotection in these subjects.

Exposure to acetaminophen impairs vasodilation, increases oxidative stress and changes arterial morphology of rats.

Acetaminophen (APAP) is one of the most widely consumed drugs in the world. Studies have shown renal and hepatic damage as the direct result of high oxidative stress induced by APAP. Since the cardiovascular system is sensitive to oxidative stress and literature describes increased cardiovascular dysfunction in APAP consumers, this work aimed to evaluate harmful effects of APAP on the vascular system. Rats were exposed to APAP (400 mg/kg/day in drinking water) for 14 days. Plasma and aortas were collected and stored in - 80 °C and a selection of arteries was prepared for isometric tension recordings, morphological, immunohistochemical and protein expression analysis. The APAP-treated group presented increased transaminases (ALT/AST) and malondialdehyde levels in the plasma compared to controls. Lipid peroxidation, glutathione reductase and superoxide dismutase levels were increased in the plasma and arteries of the APAP group. Nevertheless, glutathione level was reduced as compared to control group. The vasodilation response to acetylcholine and sodium nitroprusside (0.1 nM to 10 µM) was also impaired after APAP treatment; however, the vascular relaxation was restored after treatment with vitamin C (100 µM). Arteries from the APAP group presented reduced wall thickness, collagen deposition, elastic fibers and increased immunoreactivity to nitrotyrosine. eNOS and sGC protein expression remained unchanged and were at similar levels as controls. These findings showed higher oxidative stress and impaired vasodilation in rats exposed to APAP. Furthermore, arteries presented reduced cell layers, collagen, elastin deposition and significantly increased immunoreactivity to nitrotyrosine after APAP treatment.

Hypotensive effect and vascular relaxation in different arteries induced by the nitric oxide donor RuBPY.

NO donors are compounds that release NO that can be used when the endogenous NO bioavailability is impaired. The compound cis-[Ru(bpy)2(py)(NO2)](PF6) (RuBPY) is a nitrite-ruthenium, since it has a NO2 in its molecule. The aim of the present study was to evaluate the effect of RuBPY on arterial pressure, as well as on the vascular relaxation of different vascular arteries in renal hypertensive (2K-1C) and normotensive (2K) rats. We have evaluated the arterial pressure and heart rate changes as well as the RuBPY and SNP-induced relaxation (thoracic aorta, mesenteric resistance, coronary and basilar arteries). The administration of RuBPY in awake rats evoked a smaller but long lasting hypotensive effect when compared to SNP, with no increase in heart rate. The relaxation induced by RuBPY was similar between 2K-1C and 2K rats in thoracic aorta, mesenteric resistance and coronary arteries. However, the relaxation induced by RuBPY was smaller in basilar arteries from 2K-1C than in 2K. Taken together, our results show that RuBPY presents several advantages over SNP, since it does not induce hypotensive effect in normotensive animals, the hypotensive effect is slower, with no reflex tachycardia, and it is long lasting. In addition, RuBPY induces coronary artery relaxation (useful for angina) and presented only a small effect on basilar artery (may not induce headache).

The role of eNOS on the compensatory regulation of vascular tonus by H2S in mouse carotid arteries.

The gasotransmitter nitric oxide (NO) has an important role in vascular function and a decrease in its bioavailability is accepted as a main pathological mechanism for cardiovascular diseases. However, other gasotransmitters such as hydrogen sulfide (H2S) are also generated by the endothelium and can also affect vascular tone and a crosstalk may exist between H2S and NO. We therefore investigated the consequences of deficiency, replacement or overexpression of endothelial nitric oxide synthase (eNOS) on H2S-induced vascular responses in murine carotid arteries. In pre-contracted carotid arteries from wild-type (WT) mice, l-cysteine elicited relaxation that was inhibited by the H2S synthesis inhibitor amino-oxyacetic acid (AOAA). Genetic deletion of eNOS increased l-cysteine-induced relaxation compared to WT, but the replacement of eNOS by adenoviral transfection or H2S synthesis inhibition by AOAA reversed it. Furthermore, eNOS deletion did not alter NaHS-induced relaxation in carotid arteries while eNOS overexpression/replacement increased NaHS-induced relaxation responses in carotid arteries from WT or eNOS-/-. We suggest that, endogenously produced H2S can compensate for impaired vasodilatory responses in the absence of NO to maintain vascular patency; while, eNOS abundance can limit endogenous H2S-induced vascular responses in mice carotid arteries. Our result suggests that endogenous vs. exogenous H2S-induced relaxation are reciprocally regulated by NO in mice carotid arteries.

Relaxant effect of the prostacyclin analogue iloprost on isolated human radial artery: An approach for the reversal of graft spasm.

Radial artery graft spasm in the perioperative or postoperative period of coronary bypass surgery necessitates urgent treatment due to risk of graft failure and mortality. Herein, we evaluated the effect of iloprost, a prostacyclin (PGI2) analogue, against the contractions produced by noradrenaline and potassium chloride on isolated human radial artery. Following the determination of endothelial and vascular relaxing capacities of the arteries, iloprost (10-9M-10-6M) was cumulatively applied on rings precontracted submaximally with the spasmogens. In some rings, the response to iloprost was assessed following pretreatment with nitric oxide (NO) synthase inhibitor, l-NAME (3×10-4M,30min). Iloprost produced complete relaxations on radial artery rings precontracted with noradrenaline whereas, only moderate relaxations against the contractions induced by potassium chloride. Notably, the relaxation to iloprost was remarkably blunted in radial arteries with impaired endothelial function. Moreover, the relaxation to iloprost was unchanged in rings pretreated with l-NAME. Our results demonstrated that iloprost could be a potent relaxant agent in reversing radial artery spasm, particularly initiated by noradrenaline, possibly acting via an endothelium-mediated mechanism unrelated to NO.

Nafamostat mesilate promotes endothelium-dependent vasorelaxation via the Akt-eNOS dependent pathway.

Nafamostat mesilate (NM), a synthetic serine protease inhibitor, has anticoagulant and anti-inflammatory properties. The intracellular mediator and external anti-inflammatory external signal in the vascular wall have been reported to protect endothelial cells, in part due to nitric oxide (NO) production. This study was designed to examine whether NM exhibit endothelium dependent vascular relaxation through Akt/endothelial nitric oxide synthase (eNOS) activation and generation of NO. NM enhanced Akt/eNOS phosphorylation and NO production in a dose- and time-dependent manner in human umbilical vein endothelial cells (HUVECs) and aorta tissues obtained from rats treated with various concentrations of NM. NM concomitantly decreased arginase activity, which could increase the available arginine substrate for NO production. Moreover, we investigated whether NM increased NO bioavailability and decreased aortic relaxation response to an eNOS inhibitor in the aorta. These results suggest that NM increases NO generation via the Akt/eNOS signaling pathway, leading to endothelium-dependent vascular relaxation. Therefore, the vasorelaxing action of NM may contribute to the regulation of cardiovascular function.

Nitric oxide, endothelium-derived hyperpolarizing factor, and smooth muscle-dependent mechanisms contribute to magnesium-dependent vascular relaxation in mouse arteries.

AIM: Magnesium (Mg2+ ) is a vasorelaxant. The underlying physiological mechanisms driving this vasorelaxation remain unclear. Studies were designed to test the hypothesis that multiple signaling pathways including nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF) in endothelial cells as well as Ca2+ antagonization and TRPM7 channels in vascular smooth muscle cells mediate Mg2+ -dependent vessel relaxation. METHODS: To uncover these mechanisms, force development was measured ex vivo in aorta rings from mice using isometric wire myography. Concentration responses to Mg2+ were studied in intact and endothelium-denuded aortas. Key findings were confirmed in second-order mesenteric resistance arteries perfused ex vivo using pressure myography. Effects of Mg2+ on NO formation were measured in Chinese Hamster Ovary (CHO) cells, isolated mesenteric vessels, and mouse urine. RESULTS: Mg2+ caused a significant concentration-dependent relaxation of aorta rings. This relaxation was attenuated significantly in endothelium-denuded aortas. The endothelium-dependent portion was inhibited by NO and cGMP blockade but not by cyclooxygenase inhibition. Mg2+ stimulated local NO formation in CHO cells and isolated mesenteric vessels without changing urinary NOx levels. High extracellular Mg2+ augmented acetylcholine-induced relaxation. SKCa and IKCa channel blockers apamin and TRAM34 inhibited Mg2+ -dependent relaxation. The endothelium-independent relaxation in aorta rings was inhibited by high extracellular Ca2+ . Combined blockade of NO, SKCa , and IKCa channels significantly reduced Mg2+ -dependent dilatation in mesenteric resistance vessels. CONCLUSIONS: In mouse conductance and resistance arteries Mg2+ -induced relaxation is contributed by endothelial NO formation, EDHF pathways, antagonism of Ca2+ in smooth muscle cells, and additional unidentified mechanisms.

Vascular relaxing effect of Hydrocotyle umbellata L. is mediated by blocking of l-type Ca2+ channels.

ETHNOPHARMACOLOGICAL RELEVANCE: Hydrocotyle umbellata L. is a medicinal herb for the treatment of some health problems including hypertension, according to traditional medicine. Even so, its vascular effects and the pharmacological action mechanisms have not been analyzed. AIM OF THE STUDY: This experiment aimed to analyze the effects of hydroalcoholic extract of Hydrocotyle umbellata L. (HEHU) on isolated vessels and verify the interaction of hibalactone (chemical marker) against Cav1.2 channels using molecular docking. MATERIALS AND METHODS: Vascular reactivity experiments were performed using rat aortas with (E+) or without endothelium (E-) in an isolated organ bath. Computational molecular docking approaches were used to show the direct effect on L-type Ca2+ Channels. RESULTS: HEHU (0-560 µg/mL) induced relaxation of the pre-contracted arteries in a concentration-dependent manner. The maximum effect was higher in E+ (76.8 ± 4.1%) as compared to E- (47.3 ± 5.5%). Pre-treatment of E+ arteries with L-NAME or ODQ reduced the relaxation to similar level of E- arteries. The treatment of arteries with MDL-12,330 A, diclofenac, propranolol and atropine did not change the relaxation induced by HEHU. The contraction caused by internal Ca2+ release induced by caffeine was reduced after HEHU treatment. Moreover, the HEHU also impaired the contraction induced by Ca2+ influx stimulated with phenylephrine or high KCl. The docking study demonstrated the effectiveness of hibalactone in blocking the Cav1.2 channel. CONCLUSIONS: These findings show that HEHU induces vascular relaxation which is potentiated (but not dependent) by endothelial cells. Blocking of Ca2+ influx seems to be the main mechanism for the vascular effects of HEHU.

Perivascular adipose tissue-derived nitric oxide compensates endothelial dysfunction in aged pre-atherosclerotic apolipoprotein E-deficient rats.

BACKGROUND AND AIMS: Atherosclerosis is a major contributor to global mortality and is accompanied by vascular inflammation and endothelial dysfunction. Perivascular adipose tissue (PVAT) is an established regulator of vascular function with emerging implications in atherosclerosis. We investigated the modulation of aortic relaxation by PVAT in aged rats with apolipoprotein E deficiency (ApoE-/-) fed a high-fat diet as a model of early atherosclerosis. METHODS AND RESULTS: ApoE-/- rats (N = 7) and wild-type Sprague-Dawley controls (ApoE+/+, N = 8) received high-fat diet for 51 weeks. Hyperlipidemia was confirmed in ApoE-/- rats by elevated plasma cholesterol (p < 0.001) and triglyceride (p = 0.025) levels. Early atherosclerosis was supported by increased intima/media thickness ratio (p < 0.01) and ED1-positive macrophage influx in ApoE-/- aortic intima (p < 0.001). Inflammation in ApoE-/- PVAT was characteristic by an increased [18F]FDG uptake (p < 0.01), ED1-positive macrophage influx (p = 0.0003), mRNA expression levels of CD68 (p < 0.001) and IL-1ß (p < 0.01), and upregulated iNOS protein (p = 0.011). The mRNAs of MCP-1, IL-6 and adiponectin remained unchanged in PVAT. Aortic PVAT volume measured with micro-PET/CT was increased in ApoE-/- rats (p < 0.01). Maximal endothelium-dependent relaxation (EDR) to acetylcholine in ApoE-/- aortic rings without PVAT was severely impaired (p = 0.012) compared with controls, while ApoE-/- aortic rings with PVAT showed higher EDR than controls. All EDR responses were blocked by L-NMMA and the expression of eNOS mRNA was increased in ApoE-/- PVAT (p = 0.035). CONCLUSION: Using a rat ApoE-/- model of early atherosclerosis, we capture a novel mechanism by which inflammatory PVAT compensates severe endothelial dysfunction by contributing NO upon cholinergic stimulation.

Protective Effects of Grape Juice on Vascular Damage Induced by Chlorine Free Radical in Rats.

Grapes and their derivatives have antioxidant and cardioprotective properties. Therefore, we hypothesized that grape juice (GJ) could improve vascular oxidative damage caused by chlorine radicals (OCl-), which are excessively produced in vascular tissue during cardiovascular diseases (mainly diabetes and hypertension). The antioxidant capacity of GJ was analyzed by an electrochemical method, followed by administration in rats (100 or 300 mg/kg/d, via the oral) for seven days. Then, rats were sacrificed, and their aortas were isolated and subjected to isometric recordings or immuno-histochemical analyses with or without exposure to OCl- (5, 20, or 100 µM, 60 min). Concentration-effect curves for acetylcholine (ACh) and sodium nitroprusside (SNP) were derived to analyze endothelium-dependent or independent vasore-laxation. The GJ presented with high antioxidant capacity, and treatment with GJ did not alter vascular relaxation induced by ACh or SNP. After exposure to OCl-, endothelium-denuded arteries showed preserved relaxation with SNP, whereas endothelium-intact arteries showed reduced relaxation with ACh. OCl- at various concentrations induced significantly decreased relaxation of arteries (80.6±4.2%, 55.4±4.7%, and 28.1±5.9%, respectively) vs. control arteries (96.8±2.4%). However, treatment with GJ prevented loss in relaxation caused by 5 and 20 µM OCl- and improved relaxation after exposure to 100 µM OCl-. Exposure to OCl- induced increased nitrotyrosine immunostaining of endothelial cell layers, which was improved by GJ treatment. Altogether, vascular damage caused by OCl- was prevented by treatment with GJ, and GJ prevented nitrosative stress in these vessels.